A Vertical Shaft Impact (VSI) crusher is a particular type of crusher that is used in the production of aggregate.
A VSI crusher includes a rotor configured to rotate within a crushing chamber at high speeds about a vertical axis. Rock material enters the rotor by an inlet port and, as the rotor spins, is ejected from the rotor via outlet ports arranged about the circumference of the rotor and is hurled against anvils placed strategically about the chamber or the rock lined shell of the crusher chamber.
The impact forces breaks down the ejected rock material into aggregate. A crusher which uses this mode of breaking down rock material is sometimes known as a “rock on rock” crusher.
Some VSI crushers create impact forces by ejecting rock material from the rotor into a cascade of rock material that falls past the outlet ports of the rotor. An example of such a crusher is described in New Zealand Patent No. 297910.
Regardless of the mode of action of the rock crusher, the rotor body and its constituent components are exposed to considerable wear and tear due to the impact of the rock material entering the rotor, and the speeds at which the rotor operates.
A conventional VSI rotor consists of a one piece steel fabricated rotor body. The body includes an inlet port, outlet ports, a base plate and a top plate. The various outlet ports are formed by bolting or welding vertical members between the top and base plates. The rotor body is then protected by a number of wear resistant castings fixed about the rotor using a variety of methods.
It is not uncommon to have over 40 wear resistant components, or wear parts, protecting the rotor body. Many of these are what are referred to in the industry as rotor tips or cavity wear plates. The rotor tips are often placed at the exit of the outlet ports of the rotor body. It is usually these wear parts which experience the greatest wear and tear.
Such wear parts are typically attached to the rotor through the use of bolts or similar fasteners. These fasteners are often subject to wear and tear, and can become hard to remove. This can prolong the time the rotor is offline for maintenance.
For particularly difficult fasteners, it may be necessary to use cutting tools to allow the wear parts to be replaced. This introduces additional health and safety risks for the person using the cutting tool. This can also add to the time required for maintenance of the rotor.
In order to replace the rotor tips or cavity wear plates, it is often necessary to partially dissemble the rotor body by removing other rotor wear parts. This is a cumbersome and time consuming task.
Despite the provision of doors on the crushing chamber, it is usually still necessary to remove the roof of the crusher in order to gain access to the rotor body and allow the disassembly of the rotor body.
In order to achieve the necessary maintenance of the crusher, it must be shut down. VSI crushers are significant items of machinery, processing large amounts of rock material. The running costs of such VSI crushers can be particularly significant. Because of the expenditure associated with the purchase of crushers, and their running costs, operators tend to maximise their use where possible.
Thus, it is undesirable to have a VSI crusher offline for extended periods of time in order to fulfill maintenance requirements. The downtime of a crusher can have an impact on the throughput of the facility in which the crusher is installed. If the VSI crusher does need to be offline, then the downtime should be preferably kept to a minimum.
Furthermore, significant disassembly of the rotor often requires several persons and heavy lifting equipment in order to remove the roof and possibly other components of the crusher. This is not ideal and is not conducive to keeping maintenance costs to a minimum.
VSI crushers are also used in mineral material processing plants, such as mobile crushing plants, which combine the crusher with a feeding device, such as a conveyor or hopper, on a heavy vehicle. When replacing wear parts on these crushers, not only does the rotor body of the crusher have to partially disassembled but it is often necessary to remove the surrounding ancillary equipment as well. This extends the overall time required to replace the wear part.
It is an object of the present invention to address the foregoing problems or at least to provide the public with a useful choice.
Further aspects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only.
All references, including any patents or patent applications cited in this specification are hereby incorporated by reference. No admission is made that any reference constitutes prior art. The discussion of the references states what their authors assert, and the applicants reserve the right to challenge the accuracy and pertinency of the cited documents. It will be clearly understood that, although a number of prior art publications may be referred to herein, this reference does not constitute an admission that any of these documents form part of the common general knowledge in the art, in New Zealand or in any other country.
It is acknowledged that the term ‘comprise’ may, under varying jurisdictions, be attributed with either an exclusive or an inclusive meaning. For the purpose of this specification, and unless otherwise noted, the term ‘comprise’ shall have an inclusive meaning—i.e. that it will be taken to mean an inclusion of not only the listed components it directly references, but also other non-specified components or elements. This rationale will also be used when the term ‘comprised’ or ‘comprising’ is used in relation to one or more steps in a method or process.